(I) Basic knowledge and classification of GPS antenna
1. Function of GPS antenna
To convert the electromagnetic waves emitted by satellites into electric currents, GPS signals are circularly polarized, so all antennas work in a circularly polarized manner.
GPS antennas are divided into internal and external antennas according to their positions, among which the internal antenna is divided into passive antenna and active antenna.
GPS satellite signals are divided into L1 and L2, with frequencies of 1575.42mhz and 1228MHZ respectively. L1 is an open civil signal and the signal is circular polarization.The signal strength is about -166dbm, which is a relatively weak signal.These characteristics determine that special antennas should be prepared for THE reception of GPS signals.
1.1 Passive antenna
For example, flat plate antenna, mainly ceramic medium, is mostly square design, size is 25*25 to 12*12MM, the larger the area, the higher the resonance frequency, because no power supply, so called passive antenna.As shown in figure:
The silver layer:
The silver layer on the surface of the ceramic antenna can affect the resonant frequency of the antenna. The ideal frequency point is 1574.42mhz. In the time production, the shape of the silver surface can be adjusted to frequency modulation point.
The quality of ceramic powder and sintering process have a direct impact on its performance. The sizes of ceramic sheets on the market are mainly 25*25,18*18,15*15, 12*12, etc. The larger the area of ceramic sheets, the higher the resonance frequency.
1.2 Active antenna
As the name suggests is to power the antenna module, is composed of ceramic antenna, LNA (low noise signal module), cable, connector, plus a sealed waterproof
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